replace old %-formatted and .format(…) strings with f-strings (#7671)

mostly using flynt
https://github.com/ikamensh/flynt

gallery_dl/extractor/slideshare.py

@@ -26,8 +26,7 @@ class SlidesharePresentationExtractor(GalleryExtractor):
 
     def __init__(self, match):
         self.user, self.presentation = match.groups()
-        url = "https://www.slideshare.net/{}/{}".format(
-            self.user, self.presentation)
+        url = f"https://www.slideshare.net/{self.user}/{self.presentation}"
         GalleryExtractor.__init__(self, match, url)
 
     def metadata(self, page):
@@ -47,11 +46,8 @@ class SlidesharePresentationExtractor(GalleryExtractor):
 
     def images(self, page):
         slides = self.slideshow["slides"]
-        begin = "{}/{}/95/{}-".format(
-            slides["host"],
-            slides["imageLocation"],
-            slides["title"],
-        )
+        begin = (f"{slides['host']}/{slides['imageLocation']}"
+                 f"/95/{slides['title']}-")
         end = "-1024.jpg"
 
         return [